Specific examples of motor vehicle control systems are ABS systems for preventing locking of the wheels of a motor vehicle during braking, and ASR (traction control) systems for regulating drive slip of the drive wheels of a vehicle during acceleration. In such systems usually a regulating procedure is installed wherein the rotational velocity values of the wheels obtained by rotational-velocity sensors are processed as signals (especially information signals). When certain differences between the signals occur, control steps are triggered in the control system by means of which regulation, undesirable critical travel conditions of the vehicles are avoided. Since a closed loop control environment is involved in this case, the execution of these control steps also has a (feedback) effect on the above-mentioned signals. For instance, in case of drive slip regulation, when a spinning wheel is detected, the braking system assigned to this wheel is actuated so that the spinning tendency of the wheel is reduced.
It may however occur that differences between the signals are produced which are not caused by undesirable, critical travel conditions and which therefore should not trigger the controls. Thus for example, tires of unequal sizes or tires with unequal degrees of wear cause unequal rotational velocity signals to be produced at the rotational-velocity sensors without any locking tendency or spinning of the wheel occurring.
In order to avoid an undesirable actuation of the controls due to the above-mentioned tire differences, DE 41 14 047 A1, for example proposes an electronic braking or starting control system for vehicles which, upon recognizing such differences, computes an adaptation of the rotational velocity signals to each other. For this, and over a certain period of time that is relatively long for reasons of safety, the deviations among the rotational velocity signals are observed and a decision is made upon evaluation of the observed signal courses, on whether a deviation has occurred due to inequalities in tires. In this case the deviant rotational velocity signal is adjusted in further operation of the system through computation to another, non-deviant, observed rotational velocity signal. No progression by degrees of this adjustment is used in view of the fact that the signals are adjusted to each other at least in part relatively quickly.
The technical problem described before as an example always occurs in a general form when a signal to be processed in a method for signal processing normally shows values which are within a certain value range, called the basic value range, and when the signal can exceptionally take on certain values outside the basic value range, causing special control steps to be carried out. In this case, the special control steps should however not be carried out due to an implausible deviation of thee signal from the basic value range which may be caused, e.g., by a faulty signal calibration or by inequalities in the tires in the example of an electronic braking or starting control system for vehicles.
It is therefore the object of the present invention to rapidly recognize an implausible deviation of the signal as described above from the basic value range and to reduce or entirely prevent the undesirable effect of this deviation at an early point in time.
In the explanations below a signal is the course in time of a variable magnitude which has an amplitude value at any given point in time. The amplitude value is called the value of the signal. In case of a discrete-time signal, the sequence of individual amplitude values is designated as the signal.
A preferred area of application of the invention is in the electronic control and regulating systems in vehicles. As can be seen in the examples given in the description, the invention can also be used advantageously in other areas.